Diagnosis and treatment of autoantibody-mediated heart disease

ABSTRACT

Provided herein are, inter alia, methods of diagnosing and treating autoimmune cardiomyopathy in subjects, based upon the detection of IgG4 antibodies to cardiac autoantigens.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with Government support under Grant No. RO1HL077554 awarded by the National Institutes of Health. The Governmenthas certain rights in the invention.

TECHNICAL FIELD

This invention relates to methods of diagnosing and treating autoimmunemediated heart disease, e.g., cardiomyopathy or cardiac arrhythmias, insubjects.

BACKGROUND

Cardiomyopathy is a disease that weakens and enlarges heart muscle, andcan lead to heart failure. Heart failure is the most common hospitaldischarge diagnosis and accounts in the United States. Dilatedcardiomyopathy (DCM) is a relatively common condition (estimatedprevalence 1:2500) 36.5 per 100,000 in Olmsted County, Minn. (Cetta andMichels, Ann. Med. 27, 169-173 1995) and is the third leading cause ofheart failure. The clinical course of DCM is usually one of inexorabledecline punctuated by acute decompensation. As a result, DCM remains themost frequent indication for cardiac transplantation. Despite the highmortality, morbidity and costs associated with DCM, the pathophysiologyof this condition is largely unknown, and almost half do not have anidentifiable etiology and are labeled as having idiopathic DCM (Felker,G M et al, Medicine 78(4): 270-283, 1999). Current management of DCMprovides only supportive therapy rather than treating an underlyingcause. As a result, once heart failure is established in a patient withDCM, the expected outcome is poor, with a 5 year mortality of about 46%(Felker et al., The New England journal of medicine. 2000;342:1077-1084).

SUMMARY

The present invention is based, at least in part, on the discovery ofthe presence of IgG4 subclass autoantibodies to cardiac troponin I inhuman patients who have autoimmune heart disease, e.g., arrhythmiaand/or cardiomyopathy, and that such patient(s) can benefit fromimmunotherapy. Accordingly, provided herein are methods for diagnosingand treating autoimmune heart disease in a subject.

In one aspect, provided herein are methods for diagnosing autoimmuneheart disease in a subject, the method comprising: providing a samplefrom a subject who has heart disease; and detecting a level, or thepresence or absence, of IgG autoantibodies, e.g., autoantibodies of theIgG1, IgG2, IgG3, or IgG4 subclass to cardiac troponin I (cTnI) in thesample, wherein the presence of the IgG autoantibodies indicates thatthe subject has autoimmune heart disease. In some embodiments, themethods include determining whether the anti-cTnI antibodies arepredominantly (at least 50%, e.g., at least 60%, 70%, 80%, or 90%) IgG4subclass, wherein the presence of predominantly IgG4 subclass anti-cTnIantibodies indicates that the subject has autoimmune heart disease. Insome embodiments, the methods include determining the level of IgG4subclass autoantibodies to cTnI in the sample, and comparing the levelto a reference level, wherein the presence of a level of IgG4autoantibodies to cTnI above the reference level indicates that thesubject has autoimmune heart disease. Reference levels can be determinedusing epidemiological and biostatistical methods known in the art. Forexample, the reference level can represent a threshold level, abovewhich a subject has, or has an increased risk of developing, autoimmuneheart disease.

In some embodiments, the sample comprises serum from the subject. Insome embodiments, the sample comprises cardiac tissue, e.g., from abiopsy sample, e.g., an endomyocardial biopsy sample, and the methodsinclude detecting IgG autoantibodies, e.g., IgG4 subclass specificdeposition on the surface of cardiac myocytes from the subject.

In some embodiments, the subject has cardiac arrhythmia or idiopathicdilated cardiomyopathy. In some embodiments, autoantibodies that bind toepitopes within residues 127-164 of human cTnI are detected. In someembodiments, autoantibodies that bind to an epitope within residues127-136, 92-101, or 155-164 of human cTnI are detected.

In one aspect, methods for treating autoimmune heart disease, the methodcomprising: selecting a subject who has autoimmune heart disease; andadministering to the subject a therapy that depletes B lymphocytes inthe subject.

In some embodiments, the subject is selected by detecting the presenceof IgG4 autoantibodies to cardiac troponin I (cTnI) in the subject.

In another aspect, the invention provides methods for monitoring theefficacy of a treatment for autoimmune heart disease. The methodsinclude providing a first sample comprising serum of a subject;detecting a level of IgG, e.g., IgG1, IgG2, IgG3, or IgG4,autoantibodies to cardiac troponin I (cTnI) in the first sample,administering a therapy to the subject; providing a subsequent samplecomprising serum of a subject; detecting a level of IgG autoantibodiesto cTnI in the subsequent sample; and comparing the level of IgG, e.g.,IgG4, autoantibodies to cTnI in the first sample to the level of IgG,e.g., IgG4, autoantibodies to cTnI in the subsequent sample. A decreasein level of IgG, e.g., IgG4, autoantibodies to cTnI from the first tothe subsequent sample indicates that the therapy is effective.

In some embodiments, the therapy is or includes administration of aneffective amount of a treatment that reduces numbers ofantibody-producing B cells, e.g., and anti-CD20 antibody, e.g.,rituximab; in some embodiments, the therapy is or includesadministration of 375 mg/m² of rituximab i.v. weekly for four weeks. Thetherapy can also be or include treating the subject with plasmapheresisor administering intravenous immunoglobulin.

As used herein, “treatment” means any manner in which one or more of thesymptoms of a disease or disorder are ameliorated or otherwisebeneficially altered. As used herein, amelioration of the symptoms of aparticular disorder refers to any lessening, whether permanent ortemporary, lasting or transient that can be attributed to or associatedwith treatment by the compositions and methods of the present invention.

The terms “effective amount” and “effective to treat,” as used herein,refer to an amount or a concentration of one or more compounds or apharmaceutical composition described herein utilized for a period oftime (including acute or chronic administration and periodic orcontinuous administration) that is effective for treatingautoimmunity-mediated heart disease, e.g., for reducing one or moresymptoms or clinical signs, and returning the subject to normal or morenormal cardiac function. In addition, in some embodiments the methods oftreatment may reduce levels of IgG, e.g., IgG1, IgG2, IgG3, or IgG4autoantibodies, e.g., circulating levels of IgG autoantibodies.

Effective amounts of one or more compounds or a pharmaceuticalcomposition for use in the present invention include amounts that treatautoimmune-mediated heart disease, e.g., prevent or delay the onset,delay or halt the progression, ameliorate the effects of, or generallyimprove the prognosis of a subject diagnosed with e.g.,autoimmune-mediated heart disease. For example, in the treatment ofautoimmune-mediated heart disease, a compound which improves survival orcardiac function, or decreases the level of IgG, e.g., IgG4,autoantibodies to cardiac troponin I to any degree or delays or arrestsany symptom of autoimmune-mediated heart disease would betherapeutically effective. Since advanced heart failure withirreversible heart damage may already be present at onset of therapy, atherapeutically effective amount of a compound is not required to cure adisease but will provide a treatment for a disease. The term “subject”is used throughout the specification to describe an animal, human ornon-human, to whom treatment according to the methods of the presentinvention is provided. Veterinary and non-veterinary applications arecontemplated. The term includes, but is not limited to, mammals, e.g.,humans, other primates, pigs, rodents such as mice and rats, rabbits,guinea pigs, hamsters, cows, horses, cats, dogs, sheep and goats.Typical subjects include humans, farm animals, and domestic pets such ascats and dogs.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Methods and materials aredescribed herein for use in the present invention; other, suitablemethods and materials known in the art can also be used. The materials,methods, and examples are illustrative only and not intended to belimiting. All publications, patent applications, patents, sequences,database entries, and other references mentioned herein are incorporatedby reference in their entirety. In case of conflict, the presentspecification, including definitions, will control.

Other features and advantages of the invention will be apparent from thefollowing detailed description and figures, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1A is a pair of immunoblots showing that a subject withcardiomyopathy had autoantibodies to cardiac troponin I, and that thesecTnI autoantibodies can be greatly reduced or removed from the serum bypre-absorption (“competition”) with recombinant human troponin Iprotein.

FIG. 1B is a trio of immunofluorescence images showing that serum fromthe patient shown in 1A (left panel; green in original) stains normalhuman ventricle muscle tissue in a pattern identical to that of acommercial ventricle monoclonal antibody to cardiac troponin I (shown inthe middle panel; red in original). The right panel shows a merged image(yellow in original). These co-localization studies confirm that serumsamples from the patient and the anti-cTnI mAb identify the sameprotein, i.e., cTnI.

FIG. 1C is an image of an immunoblot showing that, in the same patientshown in FIG. 1A, cTnI autoantibodies are predominantly of the IgG4subclass (top row). This is in contrast to the expected IgG1 cTnIautoantibodies from a patient with giant-cell myocarditis, which isconsidered to be primarily a T-cell mediated autoimmune condition (shownin the middle row). No autoantibodies were detected in healthy controlserum.

FIG. 1D shows that although IgG4 is a rare subclass and comprised only3.4% of the patient's total circulating IgGs (data not shown; normalrange of serum IgG4=3-6% of total IgG), the patient's cardiac immunedeposits contained predominantly IgG4-subclass antibodies.

FIG. 1E shows that the patient's IgG4 autoantibody titers increased overtime; this was consistent with the worsening disease and decrease incardiac function seen clinically.

FIG. 1F is a photomicrograph showing immunogold staining of IgGautoantibodies deposited on tissue from an endocardial biopsy fromsubject H105 (left and middle) and control stain (right).

FIG. 2A is an immunoblot (top) and cholesterol assay (bottom) showingthe biochemical localization of TnI to a cardiomyocyte lipid-richmembrane fraction (#5) rich enriched in caveolin 3, Na/K ATPase andother signaling proteins that play a crucial role in cardiaccontractility.

FIG. 2B is an immunoblot showing that the patient's cTnI canimmunoprecipitate cTnI from the same membrane fraction #5 isolated fromheart cells.

FIG. 2C is a line graph of myocyte length and a pair of bar graphsshowing contractility and calcium transients in the presence (“Pt”) orhealthy control (“Control”) immunoglobulins. Treatment with thepatient's autoantibodies impaired the contractility of isolatedcardiomyocytes.

FIG. 3A is a pair of line graphs showing the changes in B cell numbersand cTnI autoantibody titers in response to Rituximab therapyadministered in November-December 2009.

FIG. 3B is a trio of bar graphs showing that Rituximab therapy,administered in November-December 2009 resulted in a sustained decreasein the patient's anti-cTnI IgG4 autoantibodies (top graph), but did notaffect his GAD65 (IgG1) autoantibodies (middle graph) or protectiveanti-measles antibodies (bottom graph).

FIG. 4 is a western blot and a dot plot showing that the TnIautoantibody-positive patients contain autoatibodies that arepredominantly of the IgG4 subclass. As expected these autoantibodies arenot detected in serum from healthy control subjects.

FIG. 5 is a bar graph showing detection of autoantibodies to cardiacmyosin or troponin I in a cohort of cardiomyopathy patients.

FIG. 6 is dot blot data demonstrating that the autoantibodies found insubjects recognized specific epitopes in human cardiac troponin Iprotein (SEQ ID NO:1).

DETAILED DESCRIPTION

The importance of autoimmunity in the pathogenesis of heart disease hasbeen uncertain because of a lack of reliable serological assays that candefine autoimmune heart disorders with the same sensitivity andspecificity that are available for other autoimmune diseases. Datadescribed herein suggest that patients with heart disease who havehigh-affinity autoantibodies to cardiac troponin I as detected byfluid-phase radioimmunoassay represent a distinct heart failurephenotype that could be treated with immunotherapy, e.g., B-celltargeted immunotherapy.

Accordingly, described herein are methods for diagnosing autoimmuneheart disease in subjects by detecting the presence or absence of IgG,e.g., IgG4, autoantibodies to cardiac troponin I (cTnI). Subjects whohave been diagnosed as having autoimmune heart disease can be treatedwith immunotherapy, e.g., the B-cell targeted immunotherapy describedherein. Methods for treating autoimmune heart disease are also provided.

IgG4 Subclass Antibodies

IgG4 are the rarest of the human IgG subclasses, accounting for only3-6% of total serum IgG. They are strongly linked to antibody-mediatedautoimmune diseases, e.g., idiopathic membranous nephropathy (Beck etal., N Engl J Med 2009; 361(1):11-21), pemphigus (Bhol et al.,Proceedings of the National Academy of Sciences of the United States ofAmerica 1995; 92(11):5239-43) and hyperparathyoidism due to antibodiesagainst the calcium-sensing receptor (Pallais et al., N Engl J Med 2004;351(4):362-9). The target antigens of IgG4-mediated autoimmune diseasesare generally expressed on the cell surface or extracellularly wherethey are accessible to antibodies; for example, in pemphigus, theautoantigen is desmoglein-3 (Stanley and Amagai, N Engl J Med 2006;355(17):1800-10); in idiopathic membranous nephropathy, the autoantigenis phospholipase A2 receptor (Beck et al., N Engl J Med 2009;361(1):11-21). IgG4 subclass autoantibodies to cardiac autoantigens havenot previously been described in heart failure patients.

Diagnostic Methods

Provided herein are methods for diagnosing whether a subject's heartdisease is related to or mediated by autoimmunity. The diagnosticmethods include detecting the presence or absence of IgG, e.g., IgG4autoantibodies to cTnI in a subject who has heart disease. The presenceof IgG, e.g., IgG4 subclass autoantibodies to a cardiac autoantigenindicates that the subject has autoimmune heart disease (e.g., cardiacarrhythmia, heart failure, or cardiomyopathy mediated by or associatedwith the presence of autoantibodies).

In some embodiments, IgG, e.g., IgG4, autoantibodies to specificepitopes within cTnI are detected. For example, autoantibodies thatrecognize epitopes within residues 127-164 or 92-164 of human cTnI canbe detected using, e.g., a peptide comprising residues 127-164 or92-164. In some embodiments, autoantibodies that recognize an epitopewithin residues 127-136, 92-101, or 155-164 of human cTnI are detectedusing, e.g., a peptide comprising residues 127-136, 92-101, or 155-164.Since most bone-fide autoantibody-mediated diseases are characterized byhigh-affinity autoantibodies to a narrow range of epitopes (Vinuesa etal., Nat Rev Immunol. 2009 December; 9(12):845-57), knowledge thatsubjects have restricted recognition of cTnI is useful in deciding whichpatients are most likely to be responsive to rituximab.

In some embodiments, an initial screening is done using a full-lengthcTnI, e.g., in a fluid-phase (e.g., radioimmunoprecipitation assay)format, to detect the presence of anti-cTnI antibodies. This format ispreferred to detect high-affinity autoantibodies that are often involvedin autoimmune disease. A second screen for IgG, e.g., IgG4, antibodiescould then be done, e.g., by Western blotting, radioimmunprecipitationassay, or ELISA.

Once it has been determined that a subject has autoimmune heart disease,the information can be used in a variety of ways. For example, adecision to administer a B-cell specific immunomodulatory treatment,e.g., the treatment described herein, can be made.

The methods described herein are useful in a wide variety of clinicalcontexts. For example, the methods can be used for diagnosing subjectsin hospitals and outpatient clinics, as well as the EmergencyDepartment. The methods can be carried out on-site or in an off-sitelaboratory.

Cardiac Troponin I

Cardiac troponin I (cTnI) polypeptides or immunogenic fragments thereofand nucleic acids encoding cardiac TnI polypeptides or immunogenicfragments thereof are useful in the methods described herein. Exemplarycardiac TnI amino acid sequences can be found at, e.g., GenbankAccession Nos. NP_(—)000354.4 (human; set forth as SEQ ID NO:1 in FIG.5) and NP_(—)033432.1 (mouse). Exemplary cardiac TnI nucleic acidsequences can be found at Genbank Accession Nos. NM_(—)000363.4 (human)and NM_(—)009406.3 (mouse). Immunogenic fragments can include aminoacids 92-164, 127-164, 127-136, 92-101, or 155-164 of SEQ ID NO:1.

A nucleic acid encoding a mammalian, e.g., human, cTnI amino acidsequence can be amplified from human cDNA by conventional PCRtechniques, using primers upstream and downstream of the codingsequence.

One method for producing cTnI polypeptides or fragments thereof for usein the invention is recombinant expression, which typically involves invitro translation and transcription from a recombinant nucleic acidexpression vector encoding a cTnI cDNA or portion thereof. Guidanceconcerning recombinant DNA technology can be found in numerouswell-known references, including Sambrook et al., 2001, “MolecularCloning—A Laboratory Manual,” 3d Ed. Cold Spring Harbor Press; andAusubel et al. (eds.), 2002, “Short Protocols in Molecular Biology,”John Wiley & Sons, Inc.

Purification of recombinant cTnI polypeptides or fragments thereof canbe performed by conventional methods and is within ordinary skill in theart. The purification can include two or more steps, and one step can beaffinity chromatography employing anti-cTnI antibodies covalently linkedto a solid phase chromatography support (beads) such as crosslinkedagarose or polyacrylamide. Other useful purification steps include gelfiltration chromatography and ion exchange chromatography. Purified cTnIpolypeptides and fragments thereof are also commercially available(e.g., from Sigma-Genosys, Biolegend, or Abcam).

Detecting Autoantibodies

Methods known in the art or described herein can be used to detect thepresence or absence of IgG, e.g., IgG4 autoantibodies to cardiacautoantigens. In some embodiments, serum samples from subjects arecontacted with a cardiac autoantigen, e.g., cTnI or alpha-myosin heavychain polypeptide, or an immunogenic fragment thereof, for a sufficientamount of time and under conditions that allow binding of the cardiacantigens to any autoantibodies in the serum samples. Binding occursbetween the cTnI polypeptide or fragment thereof and the autoantibodiesare then detected and, in some embodiments, quantified. In someembodiments, the autoantibodies are isolated and the presence of IgG,e.g., IgG4 subclass antibodies is detected, and, in some embodiments,quantified.

In some embodiments, biopsy samples are contacted with subclass-specificbinding reagents, e.g., antibodies that bind specifically to IgG4(and/or optionally one or more other subclasses, e.g., IgG1, IgG2, orIgG3), and the presence (and optionally, quantity) of IgG4 antibodies.

For example, enzyme-linked immunosorbent assay (ELISA) can be used todetect the presence of autoantibodies in the serum of subjects. ELISAcan detect autoantibodies that bind to antigens immobilized on solidsupport (e.g., a multi-well plate) by using enzyme-linked secondaryantibodies, such as goat anti-human Ig Abs, and enzyme substrates thatchange color in the presence of enzyme-labeled antibodies. Fluid-phaseradioimmunoassays (RIA) can also be used to detect the presence ofautoantibodies. For example, the gene for the antigen can be cloned intoan expression vector, and in vitro translation can be carried out with[³⁵S]methionine to produce radiolabeled antigens. Antibody-boundradiolabeled antigens can be separated from free radiolabeled antigenswith, e.g., protein A-Sepharose or protein G-Sepharose beads, which bindto the antibodies. To detect the presence of a specific subclass ofautoantibodies, e.g., IgG1, IgG2, IgG3 or IgG4 antibodies, anti-IgG1,IgG2, IgG3, or IgG4 antibodies can be used. For example, mouseanti-human IgG4 antibodies (available from, e.g., Sigma) bound toSepharose beads can be employed in RIA to detect subclass-specificautoantibodies in samples from a human subject using radioactive-labeledantigens and detecting specific immunocomplexes using a liquidscintillation counter. Other methods known in the art or describedherein can be used to detect the presence of autoantibodies.

Subjects

The presence of autoimmune heart disease can be detected in a subjectwith cardiomyopathy, e.g., ischemic, dilated, hypertrophic, idiopathic,or restrictive cardiomyopathy; a subject with unexplained cardiacarrhythmias; or a subject with heart failure, e.g., unexplained heartfailure; using methods described herein. Those of ordinary skill in theart would be able to determine whether a subject has cardiomyopathy,cardiac arrhythmia, or heart failure, using methods and knowledge knownin the art (see, e.g., Wynne and Braunwald, “The cardiomyopathies andmyocarditides.” In: Braunwald E., Zipes D. P., P. L, eds. Heart disease:a textbook of cardiovascular medicine. 6th ed. Philadelphia: W.B.Saunders Company; 2001: 1751-806).

In addition, the presence of autoimmune heart disease can be detectedusing the methods described herein in subjects who are asymptomatic, orsubjects who are asymptomatic relatives of affected patients.

Therapeutic Methods

Data described herein suggest that a subject who suffersautoimmune-mediated heart disease will benefit from immunotherapy. Inparticular, these subjects may benefit from agents that target Blymphocytes, which make antibodies. Accordingly, the present therapeuticmethods can include selecting a subject who has autoimmune heartdisease, and administering to the subject an effective amount of animmunotherapy. In some embodiments, the methods include administering acompound that decreases B lymphocytes, e.g., employing a directdepletion approach by engagement of B cell surface molecules, e.g.,CD19, CD20, or CD200, e.g., with an anti-CD20 monoclonal antibody (e.g.,rituximab), an anti-CD19 monoclonal antibody (e.g., XmAb5574 (MOR208;Xencor, Monrovia Calif.) or MDX-1342 (Medarex, Princeton, N.J.)), ananti-CD22 monoclonal antibody (e.g., epratuzumab); or an indirectattrition by inhibition of survival by neutralization of B lymphocytestimulator (BLyS), a potent B cell survival factor (e.g., usinganti-BLyS/BAFF agents such as belimumab or atacicept). In someembodiments, the methods include administering, in addition to or as analternative to rituximab, Azathioprine; a steroid such as cyclosporineor methylprednisolone; Immunoadsorption (IAS)/plasmapheresis. See, e.g.,Engel et al., Pharmacol Rev. 2011 March; 63(1):127-56. Epub 2011 Jan.18; Stohl and Looney, Clin Immunol. 2006 October; 121(1):1-12. Epub 2006May 11; Stummvoll et al., Atheroscler Suppl. 2009 Dec. 29; 10(5):110-3;and Vaughan et al., Int J Biochem Cell Biol. 2011 March; 43(3):280-5.Epub 2010 Dec. 13.

In patients with rheumatoid arthritis treated with rituximab, clinicalrelapse was preceded by a rise in autoantibody levels and B cellsreappeared at a mean of 8 months after treatment (Leandro et al.,Arthritis Rheum 2006; 54(2):613-20). In contrast, in severe pemphigusassociated with IgG4 autoantibodies, 86% of subjects treated withrituximab remained in complete remission almost after mean follow-up of34 months suggesting that in some autoimmune conditions, remissions canbe sustained (Joly et al., N Engl J Med 2007; 357(6):545-52). The use ofrituximab for cardiomyopathy has not previously been described.

The treatment methods described herein can be combined with otherimmunotherapy, e.g., plasmapheresis to remove the autoantibodiestypically with supplemental administration of intravenous immunoglobulin(IVIg). Two methods are typically used in plasmapheresis to separateplasma from blood cells: membrane filtration and extracorporealcentrifugation. Both techniques are designed to remove large molecularweight substances, such as antibodies, from the plasma. IVIg is amixture of proteins containing y-globulins, predominantly IgG, toprovide passive, temporary humoral immunity against disease. Othertreatments for heart disease can also be administered.

Subject Selection

The present treatments methods can be used to treat subjects who haveautoimmune heart disease, e.g., subjects whose heart disease has beendiagnosed as mediated by or related to autoimmunity, e.g., by a methoddescribed herein. Thus the methods can include detecting the presence ofautoimmune heart disease in a subject using a method described herein,and administering to the subject a therapeutically effective amount ofan agent described herein, e.g., agents that target B lymphocytes, e.g.,rituximab.

Monitoring of Treatment

Effectiveness of the treatment methods described herein can bedetermined by monitoring changes in the cardiac symptoms, characteristicfeatures, or parameters of the subject being treated. For the methodsdescribed herein, it may be useful to monitor the level of IgG, e.g.,IgG4, autoantibodies to cTnI in the subject, e.g., before, throughout,and after the treatment. Evaluation by endomyocardial biopsy couldinclude examination for one or both of total IgG and IgG subclassdeposition.

Pharmaceutical Compositions and Methods of Administration

The compounds and compositions described herein can be administered to asubject, e.g., a subject identified as being in need of treatment, usinga systemic route of administration. Systemic routes of administrationcan include, but are not limited to, parenteral routes ofadministration, e.g., intravenous injection, intramuscular injection,and intraperitoneal injection; enteral routes of administration, e.g.,administration by the oral route, lozenges, compressed tablets, pills,tablets, capsules, drops (e.g., ear drops), syrups, suspensions andemulsions; transdermal routes of administration; and inhalation (e.g.,nasal sprays).

In some embodiments, the modes of administration described above may becombined in any order and can be simultaneous or interspersed.

Pharmaceutical compositions typically include a pharmaceuticallyacceptable carrier. As used herein the language “pharmaceuticallyacceptable carrier” includes saline, solvents, dispersion media,coatings, antibacterial and antifungal agents, isotonic and absorptiondelaying agents, and the like, compatible with pharmaceuticaladministration.

Pharmaceutical compositions are typically formulated to be compatiblewith its intended route of administration. Examples of routes ofadministration include parenteral, e.g., intravenous, intradermal,subcutaneous, oral (e.g., inhalation), transdermal (topical),transmucosal, and rectal administration.

Methods of formulating suitable pharmaceutical compositions are known inthe art, see, e.g., the books in the series Drugs and the PharmaceuticalSciences: a Series of Textbooks and Monographs (Dekker, NY). Forexample, solutions or suspensions used for parenteral, intradermal, orsubcutaneous application can include the following components: a sterilediluent such as water for injection, saline solution, fixed oils,polyethylene glycols, glycerine, propylene glycol or other syntheticsolvents; antibacterial agents such as benzyl alcohol or methylparabens; antioxidants such as ascorbic acid or sodium bisulfite;chelating agents such as ethylenediaminetetraacetic acid; buffers suchas acetates, citrates or phosphates and agents for the adjustment oftonicity such as sodium chloride or dextrose. pH can be adjusted withacids or bases, such as hydrochloric acid or sodium hydroxide. Theparenteral preparation can be enclosed in ampoules, disposable syringesor multiple dose vials made of glass or plastic.

Pharmaceutical compositions suitable for injectable use can includesterile aqueous solutions (where water soluble) or dispersions andsterile powders for the extemporaneous preparation of sterile injectablesolutions or dispersion. For intravenous administration, suitablecarriers include physiological saline, bacteriostatic water, CremophorEL™ (BASF, Parsippany, N.J.) or phosphate buffered saline (PBS). In allcases, the composition must be sterile and should be fluid to the extentthat easy syringability exists. It should be stable under the conditionsof manufacture and storage and must be preserved against thecontaminating action of microorganisms such as bacteria and fungi. Thecarrier can be a solvent or dispersion medium containing, for example,water, ethanol, polyol (for example, glycerol, propylene glycol, andliquid polyetheylene glycol, and the like), and suitable mixturesthereof. The proper fluidity can be maintained, for example, by the useof a coating such as lecithin, by the maintenance of the requiredparticle size in the case of dispersion and by the use of surfactants.Prevention of the action of microorganisms can be achieved by variousantibacterial and antifungal agents, for example, parabens,chlorobutanol, phenol, ascorbic acid, thimerosal, and the like. In manycases, it will be preferable to include isotonic agents, for example,sugars, polyalcohols such as mannitol, sorbitol, sodium chloride in thecomposition. Prolonged absorption of the injectable compositions can bebrought about by including in the composition an agent that delaysabsorption, for example, aluminum monostearate and gelatin.

Sterile injectable solutions can be prepared by incorporating the activecompound in the required amount in an appropriate solvent with one or acombination of ingredients enumerated above, as required, followed byfiltered sterilization. Generally, dispersions are prepared byincorporating the active compound into a sterile vehicle, which containsa basic dispersion medium and the required other ingredients from thoseenumerated above. In the case of sterile powders for the preparation ofsterile injectable solutions, the preferred methods of preparation arevacuum drying and freeze-drying, which yield a powder of the activeingredient plus any additional desired ingredient from a previouslysterile-filtered solution thereof.

Oral compositions generally include an inert diluent or an ediblecarrier. For the purpose of oral therapeutic administration, the activecompound can be incorporated with excipients and used in the form oftablets, troches, or capsules, e.g., gelatin capsules. Oral compositionscan also be prepared using a fluid carrier for use as a mouthwash.Pharmaceutically compatible binding agents, and/or adjuvant materialscan be included as part of the composition. The tablets, pills,capsules, troches and the like can contain any of the followingingredients, or compounds of a similar nature: a binder such asmicrocrystalline cellulose, gum tragacanth or gelatin; an excipient suchas starch or lactose, a disintegrating agent such as alginic acid,Primogel, or corn starch; a lubricant such as magnesium stearate orSterotes; a glidant such as colloidal silicon dioxide; a sweeteningagent such as sucrose or saccharin; or a flavoring agent such aspeppermint, methyl salicylate, or orange flavoring.

Systemic administration of a therapeutic compound as described hereincan also be by transmucosal or transdermal means. For transmucosal ortransdermal administration, penetrants appropriate to the barrier to bepermeated are used in the formulation. Such penetrants are generallyknown in the art, and include, for example, for transmucosaladministration, detergents, bile salts, and fusidic acid derivatives.Transmucosal administration can be accomplished through the use of nasalsprays or suppositories. For transdermal administration, the activecompounds are formulated into ointments, salves, gels, or creams asgenerally known in the art.

In one embodiment, the therapeutic compounds are prepared with carriersthat will protect the therapeutic compounds against rapid eliminationfrom the body, such as a controlled release formulation, includingimplants and microencapsulated delivery systems. Biodegradable,biocompatible polymers can be used, such as ethylene vinyl acetate,polyanhydrides, polyglycolic acid, collagen, polyorthoesters, andpolylactic acid. Such formulations can be prepared using standardtechniques, or obtained commercially, e.g., from Alza Corporation andNova Pharmaceuticals, Inc. Liposomal suspensions (including liposomestargeted to selected cells with monoclonal antibodies to cellularantigens) can also be used as pharmaceutically acceptable carriers.These can be prepared according to methods known to those skilled in theart, for example, as described in U.S. Pat. No. 4,522,811.

The pharmaceutical compositions can be included in a container, pack, ordispenser together with instructions for administration.

The compositions described herein can be administered one from one ormore times per day to one or more times per week; including once everyother day. The skilled artisan will appreciate that certain factors mayinfluence the dosage and timing required to effectively treat a subject,including but not limited to the severity of the disease or disorder,previous treatments, the general health and/or age of the subject, andother diseases present. Moreover, treatment of a subject with atherapeutically effective amount of the therapeutic compounds describedherein can include a single treatment or a series of treatments.

Dosage, toxicity and therapeutic efficacy of the therapeutic compoundscan be determined by standard pharmaceutical procedures in cell culturesor experimental animals, e.g., for determining the LD50 (the dose lethalto 50% of the population) and the ED50 (the dose therapeuticallyeffective in 50% of the population). The dose ratio between toxic andtherapeutic effects is the therapeutic index and it can be expressed asthe ratio LD50/ED50. Compounds which exhibit high therapeutic indicesare preferred.

The data obtained from cell culture assays and animal studies can beused in formulating a range of dosage for use in humans. The dosage ofsuch compounds lies preferably within a range of circulatingconcentrations that include the ED50 with little or no toxicity. Thedosage may vary within this range depending upon the dosage formemployed and the route of administration utilized. For any compound usedin the method of the invention, the therapeutically effective dose canbe estimated initially from cell culture assays. A dose may beformulated in animal models to achieve a circulating plasmaconcentration range that includes the IC50 (i.e., the concentration ofthe test compound which achieves a half-maximal inhibition of symptoms)as determined in cell culture. Such information can be used to moreaccurately determine useful doses in humans. Levels in plasma may bemeasured, for example, by high performance liquid chromatography.

For compounds known in the art (e.g., rituximab), practitioners mightgenerally use in humans and non-human subjects the recommended (e.g.,FDA approved) dosage for that compound.

EXAMPLES

The invention is further described in the following examples, which donot limit the scope of the invention described in the claims.

Example 1 Identification of IgG4 Autoantibodies to cTnI in HumanPatients

Evidence that autoimmune mechanisms alone can cause T1D heart disease isexemplified by a patient with T1D since age 12 yrs (“H-105”) who, at age17 yrs, presented with severe arrhythmias and unexplained dilatedcardiomyopathy with normal coronary angiography. The family history wasnotable for the presence of autoimmune diseases in multiple familymembers including a parent with T1D and thyroiditis.

A complete clinical evaluation of the patient was performed to definethe etiology of his cardiomyopathy, including EKG, chest X-ray, bloodwork, echocardiography, and cardiac MRI.

Blotting was performed to detect autoantibodies. 2.5 ug/lane of totalSDS lysates from human heart, skeletal muscle and liver or 0.25 ug/laneof purified human cTnI (Life Diagnostics) were separated in a 10%SDS-PAGE gel and transferred to nitrocellulose paper. The blots wereincubated overnight with control or patient sera diluted 1:1000,followed by incubation with peroxidase-conjugated F(ab′)2 fragment ofgoat anti-human IgG (Jackson ImmunoResearch Laboratories Inc). Blotswere developed using Western Lighting Chemiluminescence Reagent Plus(Perkin Elmer). The patient was found to have high titers ofautoantibodies directed against cTnI (FIG. 1A).

Indirect immuno-fluorescent analysis was also performed with thepatient's serum. Frozen sections from normal human donor heart embeddedin OCT were fixed in 2% paraformaldehyde and permeabilized withTX-100/PBS. After blocking, sections were incubated overnight with 1:100dilutions of serum from the patient or 1:250 dilution of mousemonoclonal anti Troponin I (SIGMA), followed by detection withFITC-conjugated mouse F(ab′)₂ anti-human IgG or FITC conjugated F(ab′)₂goat-anti mouse IgG (Jackson ImmunoResearch Laboratories Inc.). Foridentification of nuclei slides were stained with Hoechst 33258 andmounted using Fluorogel (Electron Microscopy Science). Images were takenwith an Axiocam camera linked to a Zeiss Axioscop 2 microscope. Theresults showed that the patient's autoantibodies stained the surface ofnormal hearts in a pattern indistinguishable from that seen with acommercial monoclonal antibody against human troponin I (FIG. 1B).

The circulating (serum) anti-troponin antibodies were subjected tosubclass analysis as follows. 0.25 ug/lane of purified human cTnI (LifeDiagnostics) were separated in a 10% SDS-PAGE gel and transferred tonitrocellulose paper. The blots were cut into strips and incubated withpatients or controls sera diluted 1:1000. Individual strips wereincubated with mouse antibodies against the four human IgG subclasses(Zymed laboratories). Blots were developed using Western LightingChemilumineiscence Reagent Plus (Perkin Elmer) The results showed thatthe antibodies were predominantly of the IgG4 subclass (FIG. 1C).

Standard hematoxylin and eosin staining of an endomyocardial biopsyrevealed the anticipated myocyte hypertrophy and interstitial fibrosiscompatible with an advanced cardiomyopathy. No other etiology wasidentified by the biopsy to account for the patient's condition,including myocarditis or iron deposition.

The patient's endomyocardial biopsy sample was frozen in OCT andsections were stained with mAbs against human total IgG and IgG1, IgG2,IgG3 and IgG4. Human cardiac tissues from biopsy were fixed overnight inParaformaldehyde-glutaraldehyde fixative. The tissue was cryoprotectedand embedded in OCT compound (Tissue-Tek, Sakura Finitek). Although IgG4comprised only 3.4% of his total circulating IgG using subclass-specificantibodies (Human IgG Subclass Profile ELISA kit form Zymed LaboratoriesINC, following the manufacturer's instructions; normal range ofIgG4=3-6%), the patient's heart biopsy sample demonstrated enrichedIgG4-specific Ab deposition (FIG. 1D).

IgG subclass specific cTnI antibodies were measured by incubatingpatients or controls serum with ³⁵S-labeled human cardiac troponin I inTBS-1% TX100 Buffer at 4° C. for 24 h. IgG subclass specific Ab boundSepharose beads were prepared using Biotin-labeled mouse mAbs againsthuman IgG1, IgG2, IgG4 and IgE (BD Pharmingen) and Sepharose 4Bstreptavidin beads (GE Healthcare). Aliquots of serum were spotted in a96-well filtration plate (Unifilter, Whatman) and IgG subclass specificAb beads were added and incubated for 1 h at 4° with shaking. Afterincubation the plate was washed with cold TBS-TX-100 buffer, dry and 50ul of scintillation liquid added. The radioactivity in the samples wasdetermined using a Wallac MicroBeta Scintillation Counter (PerkinElmer). Interestingly, worsening heart function with a progressivedecrease in the patient's ejection fraction from ˜50% to ˜30% correlatedwith increasing cTnI-Ab IgG4 titers over a 15-month period (FIG. 1E).

Example 2 Human Patient-Derived cTnI Autoantibodies Recognize TnI on thePlasma Membrane of Heart Cells

Specialized biochemical membrane fractionation techniques were performedas described in Head et al., JBC 281(36) 26391-26399 (2006). Briefly,mouse hearts were homogenized in ice-cold Buffer A (250 mM sucrose, 20mM Tri-HCl pH 7.4, containing freshly added protease inhibitors) using a40 ml glass Dounce homogenizer. The homogenate was centrifuge at 700g×20 min and the resulting supernatant (SN1) was centrifuged at100,000×g for 1 h. After centrifugation the pellet was resuspended in500 mM NaHCO₃ pH 11 using a glass homogenizer and mixed with 1 volume of90% sucrose in MBS buffer (25 mM MES pH 6.5, 150 mM NaCl), and layeredon a discontinuous sucrose gradient (45, 35 and 5% sucrose in MBSbuffer). After centrifugation at 280,000×g for 18 h at 4° C., 1 mlsamples were collected from the top of the gradient and analyzed byWestern Blotting using the following antibodies: mouse anti-caveolin 3(BD Transduction Laboratories), rabbit polyclonal anti ATPase beta1(Na+/K+) (GeneTex, Inc.), mouse anti human cTroponin I (clone C-4)(Santa Cruz Biotechnology Inc.), rabbit anti human c Troponin C (cloneH110) (Santa Cruz Biotechnology, Inc.) and patient purified IgG4. Thecholesterol concentration for each sample was determined using theAmplex Red Cholesterol Assay Kit (Invitrogen). A band corresponding tocTroponin I was detected in the buoyant caveolin-3 enriched membranefractions (Fraction No. 5), were also co-localized with the plasmamembrane marker ATPase beta1 (Na⁺/K⁺) that was enriched in cholesterol.Cardiac troponin I was also distributed in heavy/non buoyant fractions(Fractions 8-12) and co-localized with cTroponin C. Patient serarecognized the same antigen as the commercial antibody against cTroponinI.

FIG. 2B Fractions enriched in cTnI from the NaHCO₃ fractionationprotocol were used for immunoprecipitation analysis. Fraction 5 wasdiluted in MES buffer plus protease inhibitors (0.8 mg protein) andincubated overnight with the patient, control sera or buffer and thenwith protein A/G plus beads (Pierce). The immunocomplexes bound to thebeads were separated in a 4-15% gradient SDS-PAGE gel, transferred tonitrocellulose and probed by western blot (WB) with mouse anti humancTroponin I (clone C-4) (Santa Cruz Biotechnology Inc.). Patient serabut not control sera specifically immunoprecipitated the cTroponin Ipresent in the caveolin enriched fraction obtained by carbonatefractionation.

The results demonstrated that troponin I is found on the plasma membraneof heart cells, in addition to its expected location inside heart cells(FIGS. 2A and 2B). These results are also consistent withimmunofluorescence staining and immunogold EM studies clearly depositionof IgG4 autoantibodies on the surface of his myocardial cells.

Example 3 Human Anti-TnI IgG4 Autoantibodies Impair Cardiac Function

cTnI Abs have been shown to cause arrhythmias and dilated cardiomyopathyin mouse models (Okazaki et al., Nat Med 9, 1477-83 (2003)), raising thepossibility of a similar pathogenic process in this patient.“Pathogenicity assays” (functional assays) were performed. Myocytes fromadult rats were obtained by Langendorff-perfusion with Ca²⁺ freeTyrode's solution. Myocytes were culture and treated for 18 h withcontrol or patient sera. Ca²⁺ transients and mechanical properties wereassessed in the myocytes, which were continuously perfused in a heatedchamber with perfusion buffer (137 mM NaCl, 5.4 mM KCl, 0.5 mM MgCl₂, 10mM HEPES, 5.5 mM glucose, 1.2 mM CaCl₂, 0.5 mM probenecid) andelectrically stimulated at 0.5 Hz. Cell shorting was monitored by adigital edge detection system (IonOptix) with a sampling rate of 240 Hz.Ca²⁺ transients were measured in fura-2/AM (Molecular Probes) loadedcardiomyocytes (1 uM for 15 min at room temperature) using a dualexcitation Hyperswitch (IonOptix). Data were analyzed using the softwareIonwizard (IonOptix).

These studies were performed in infusion chambers, visualizing heartbeats of adult mouse (or rat) heart cells with the IonOptix videodetection system. The results showed that autoantibodies from patientH-105 impaired the contractility and calcium homeostasis of isolatedheart cells (FIG. 2C).

Example 4 B-Cell Depletion Therapy for Treatment of Autoimmune HeartDisease

Patient H105 completed five cycles of plasmapheresis followed byadministration of 2 g/kg intravenous immunoglobulin (IVIG). The patientwas subsequently treated with rituximab (375 mg per square meter of bodysurface area) weekly for a total of four weeks. Two years after thistreatment the patient was rated as New York Heart Association Class IIwith regard to congestive heart failure symptoms and displayed an oxygenconsumption of 19.4 ml/kg/min despite a sub-maximal effort asdemonstrated by his respiratory ratio of 0.99. The patient's estimatedpulmonary artery pressure has remained below 20 mmHg subsequent tocompletion of his therapy. The rituximab therapy has had a beneficialeffect on the patient's anti-troponin I antibody titers. The treatmenthas also has markedly improved this patient's symptoms and arrested thepreviously rapid progression of his heart failure with stabilization inhis ejection fraction and improvement of his oxygen consumption to 28ml/kg/min (at his last examination in June, 2011). There was efficientdepletion of all subpopulations of peripheral B cells, including cellswith plasma cell precursor phenotype (CD19⁺, CD20⁻, CD38⁺⁺⁺) one monthafter completing his treatment with rituximab, and this has persisted 26months post-therapy as has the reduction in his anti-troponin antibodies(FIG. 3A). This has been associated with a stabilization in his ejectionfraction to 25-30% (after a steady decline from 44% to 31% over the 2-yrperiod preceding immunotherapy) and improvement in his clinicalsymptoms.

Importantly, the rituximab therapy selectively depleted TnIautoantibodies in subject H105, but did not diminish the levels ofeither his type 1 diabetes-associated GAD 65 autoantibodies (GADA),which are not postulated to play a pathogenic role in diabetes, or thelevels of his protective antibodies to measles (FIG. 3B). Thepreservation of anti-microbial immunity may explain the lack of anyadverse side-effects (i.e., no increased susceptibility to infections)from immunotherapy. These studies suggest that rituximab therapyselectively depletes the B cells that produce pathogenic troponinautoantibodies and underscores the safety and therapeutic potential ofusing rituximab for patients with idiopathic cardiomyopathy who testpositive for troponin I autoantibodies. The ability of rituximab toselectively reduce the patient's IgG4 TnI autoantibodies suggests thatthey are derived from short-lived autoreactive plasma cells: Selectiveautoantibody depletion is noted after rituximab treatment in otherIgG4-Ab human autoimmune diseases (e.g., pemphigus, Joly et al., N EnglJ Med 2007; 357:545-52) and in autoantibody-mediated autoimmune mousemodels (Huang et al., Proc Natl Acad Sci USA. 2010 Mar. 9;107(10):4658-63. Epub 2010 Feb. 22).

Example 5 Screening Human Patients for Autoantibodies to cTnI

New screening assays using recombinantly produced human cTnI protein ina fluid-phase format, suitable for the detection of high affinityautoantibodies characteristic of organ-specific autoimmune diseases,were developed and used to screen a cohort of cardiomyopathy patients.

1. Construction of Recombinant Human cTnI:—

Total RNA was extracted from human ventricle tissue using Trizol(Invitrogen, USA) as per the manufacture's instructions. One microgramof Total RNA was used to reverse-transcribe (RT-PCR) into cDNA usingTranscriptor first strand cDNA synthesis kit (Roche, USA) according tothe manufacture's protocol.

The cDNA specific to human cardiac troponin I (cTnI) was made by PCR(FastStart High Fidelity PCR system, Roche, USA) using the followingspecific primers: Forward: 5′ TTG CAC TCG TCT AGA TGT CCT CGG GGA GTCTCA AGC 3′ and Reverse: 5′ TAC CAC GCG TCT AGA AGC TCA GAG AGA AGC TTTATT 3′. Restriction sites for XbaI (underlined in the primer sequences)were incorporated into the forward and reverse primers in order to allowsub-cloning of the PCR products into pSP64 Poly(A) expression vector(Promega, USA) and the subsequent expression of the human cTnI cDNA fromthe SP6 promoter present in the vector.

One hundred nanograms of cDNA were subjected to 35 cycles of PCRamplification in a Peltier Thermal Cycler (Biorad, USA) using thefollowing conditions: denaturation 95° C. for 30 sec, annealing 67.4° C.for 30 sec, elongation 72° C. for 1 min. The PCR products (˜837 bp) wereran on 1% agarose gel and then purified using Qiaquick gel purificationkit (Qiagen, USA). Subsequently, the purified PCR products were digestedwith XbaI (New England Biolabs, USA) and then ligated into pSP64 Poly(A)vector at XbaI site. The ligation reaction was transformed into Top 10competent cells (Invitrogen, USA) and selected the clones by platingthem onto LB agar plates containing ampicillin (Sigma) at 100 μg/ml.Successful clones were screened for by restriction digestion withHindIII (New England Biolabs, USA) and the appropriate recombinantplasmids were sequenced completely to verify that no sequence errors hadbeen introduced and also to confirm the orientation of the clone inorder to express in vitro from SP6 promoter. The recombinant plasmid,pSP64 Poly(A)+human cTnI, was purified with a QIAGEN Plasmid Maxi Kit(Qiagen, USA). This recombinant plasmid clone was used for theexpression of human cTnI protein in a cell free system.

2. Expression of Human cTnI Using Cell Free System:—

The plasmid construct (pSP64Poly(A)+human cTnI) was used in a TnT SP6Quick Coupled Transcription/Translation System (Promega, USA) to produceand label cTnI with [³⁵S]-methionine in vitro. The cTnI cDNA fragmentwas inserted into pSP64 Poly(A) in the correct orientation to allowexpression from the SP6 promoter, and each template containedappropriate start and stop codons to ensure accurate translation. Astandard reaction mixture of 50 μl contained: quick master mix, 40 μl;plasmid template, 2 μg; [³⁵5]-methionine (1000 Ci/mmol; 10 mci/ml; GEHealthcare, USA), 2 μl and made the total volume up to 50 μl with thenuclease free water. The reaction was incubated for 90 minutes at 30° C.and then stored at −20° C. until required.

An aliquot of each of the in vitro translation reaction mixtures wasadded to SDS sample buffer and boiled for 5 minutes before it ran on 10%Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE).Prior to drying under vacuum, gels were soaked in fixing solution andthen in 10% glycerol. Autoradiography was carried out at −80° C.Radioactivity incorporated into the protein was determined bytrichloroacetic acid (TCA) precipitation as per the Promega's technicalmanual.

3. Radioimmunoprecipitation Assay for the Detection of Human cTnIAutoantibodies

Patient and control sera were tested for binding to [³⁵S]-human cTnI inradio-immunoassays as follows. For each assay, an aliquot of in vitrotranslation reaction mixture (equivalent to 48,000 counts per minute(cpm) of TCA-precipitable material) was suspended in 120 μl ofimmunoprecipitation buffer containing: 20 mM Tris-HCl pH 7.4; 150 mMNaCl; 1% (v/v) Triton X-100; 10 μg/ml aprotinin (Sigma, USA). Serum wasthen added to a final dilution of 1:25 and the reaction was carried outin a microcentrifuge tube. The samples were incubated with shaking atroom temperature for 2 hrs prior to overnight incubation with shaking at4° C. All samples were tested in duplicates.

On the next day, 50 μl (20,000 cpm) of the reaction samples weretransferred to each well of the 96 well plate (Whatman, USA).Subsequently, 50 μl of protein A/G (50% A/8% G) Sepharose 4 Fast Flowbeads (GE Healthcare, USA), prepared according to the manufacturer'sprotocol, were added to each well and incubation continued for 1 hour at4° C. The protein A/G Sepharose-antibody complexes were then washedtotal of twelve times (4 times washing with 5 minutes incubation periodin between wishes) in immunoprecipitation buffer at 4° C. withvacuum-operated 96-well plate washer (Millipore, USA). At the end offinal wash, the plate was dried under lamp for 10 min and then added 100μl of MicroScint-20 scintillation cocktail (PerkinElmer, USA) into eachwell. Immunoprecipitated radioactivity was counted in a Wallac 1450microbeta Trilux liquid scintillation counter (PerkinElmer, USA). Allsamples were analyzed in duplicate and the mean cpm immunoprecipitatedwere determined.

The binding reactivity of each patient and control sera to human cTnIwas expressed as an antibody index calculated as: cpm immunoprecipitatedby tested serum divided by mean cpm immunoprecipitated by all healthycontrol sera. The upper level of normal for each assay was calculatedusing the mean antibody index+3 standard deviations (SD) of all controlsera. Patient sera with an antibody index greater than the upper levelof normal were regarded as positive for binding to the radio-labeledcTnI used in the assay.

In the heart failure cohort screened, about 20% of patients withidiopathic dilated cardiomyopathy (DCM) were positive for high-titerautoantibodies directed against cTnI (FIG. 5). Remarkably, thesepatients were also distinctive in producing predominantly IgG4 subclassanti-cTnI antibodies. Initial characterization of the fine specificitiesof the autoantibodies revealed that they target the same domain of thecTnI protein. Patients with DCM and high circulating anti-cTnIantibodies may represent a distinct heart failure phenotype that couldrespond to B-cell targeted immunotherapy.

Mean age was 48 yrs, 61% were male, and mean EF was 30% in HF patients.Anti-troponin Ab were detected more often in myocarditis and idiopathicdilated cardiomyopathy compared to other HF etiologies (20% vs. 5%,p=0.004); none were found in controls. In HF patients, anti-myosin Abwere more common than anti-troponin Ab (29% vs. 10%, p<0.0001) and wereparticularly enriched in myocarditis subjects vs. other causes of HF(p=0.007). There was little overlap between anti-myosin andanti-troponin Ab production, with 87% of Ab-positive subjects havingonly a single Ab type detected. See FIG. 5, suggesting that thedetection of cTnI autoantibodies defines a unique heart failurephenotype.

Cardiac autoantibodies are relatively common in HF; however, theirantigenic specificity varies with etiology. Troponin Ab are morespecific to both myocarditis and idiopathic dilated cardiomyopathy.Differential Ab detection may be a marker or mediator of clinical riskin a subset of inflammatory cardiomyopathies.

Example 6 Epitope Analysis for Autoantibodies to cTnI

As a first step towards identifying the epitopes recognized by cTnIautoantibodies in our patients, SPOTscan analysis Epitope mappingprotocol was performed as described in the company manual (JPT PeptideTechnologies, Germany) was used. This method has been widely used inepitope mapping of autoantigens in other human autoimmune diseases, suchas SLE and Goodpasture's syndrome.

Affinity-purified IgGs from H105 and M2 (a 21-year old patient whopresented in severe heart failure with an EF of 15% and showed thesecond highest levels of IgG4 cTnI antibody titers of the cohortstudied, see Example 5) were immunoblotted on Whatman 50 cellulosemembranes that contained 30 covalently-bound overlapping 10-mer peptidescovering the entire length of the human cTnI protein sequence(Sigma-Genosys) (FIG. 6), as follows:

These studies were remarkable in revealing that H105's autoantibodiesare essentially monospecific, recognizing only a single peptide,cTnI₁₂₇₋₁₃₆, whereas M2 serum recognized cTnI₉₂₋₁₀₁ and cTnI₁₅₅₋₁₆₄.Sera from normal controls did not react with any of the cellulose-boundcTnI peptides (FIG. 6). These peptide sequences are distinctive in beinghighly conserved across species (90-100% conservation between rodentsand humans), consistent with their important physiological roles:peptides TnI₉₂₋₁₀₁ and TnI₁₂₇₋₁₃₆ are both part of the H2 helix(residues 90-135 of cTnI) that binds to troponin T whereas TnI₁₅₅₋₁₆₄ ispart of the H3 helix that binds to troponin C (Takeda et al., Nature2003; 424(6944):35-41). Interestingly, sequence motifs residing in theH2 helix have also been recently implicated in a TnI-immunizationinduced model of murine myocarditis (Kava et al., Circulation 2008;118(20):2063-72).

Immunoassays for autoantibodies based on in vitro translation of cDNAsencoding human cardiac myosin and troponin and immunoprecipitation werealso tested with patient sera in 96-well filtration plates. Studysubjects (174 with heart failure (HF) and 74 controls) underwentcomprehensive evaluation and testing for autoantibodies and HLA-DQ/DRhaplotype. HF etiology was assigned by investigators blinded toautoimmune test results. Primary analysis compared specificautoantibodies (Ab) according to HF etiology.

Using troponin peptide mapping techniques, the precise epitopesrecognized by autoantibodies from 7 other individuals with high titersof troponin I autoantibodies were identified. Interestingly, one patient(who also had type 1 diabetes) targeted the same peptide as did patientH105 (cTnI₁₂₇₋₁₃₆), while 4 of 8 patients reacted most strongly to asingle peptide, peptide 23 (cTnI₁₅₅₋₁₆₄), and 7 of 8 patients recognizedpeptides spanning peptides 19-23 (cTnI₁₂₇₋₁₆₄). Thus, the autoantibodiesfrom our cohort targeted a similar region of the TnI protein. Thesefindings are important because in other autoimmune diseases, thepathogenicity of autoantibodies correlates closely with the epitopestargeted by autoantibodies (Bhol et al., Proceedings of the NationalAcademy of Sciences of the United States of America 1995;92(11):5239-43).

OTHER EMBODIMENTS

It is to be understood that while the invention has been described inconjunction with the detailed description thereof, the foregoingdescription is intended to illustrate and not limit the scope of theinvention, which is defined by the scope of the appended claims. Otheraspects, advantages, and modifications are within the scope of thefollowing claims.

What is claimed is:
 1. A method for diagnosing the presence of, or riskof developing, autoimmune heart disease in a subject, the methodcomprising: providing a sample comprising serum of a subject; anddetecting a level, presence, or absence in the sample of IgGautoantibodies to cardiac troponin I (cTnI), wherein the presence of IgGautoantibodies to cTnI, e.g., a level above a reference, indicates thatthe subject has or is at risk of developing autoimmune heart disease. 2.The method of claim 1, wherein the subject has cardiac arrhythmia,idiopathic dilated cardiomyopathy, ischemic cardiomyopathy orunexplained heart failure.
 3. The method of claim 1, whereinautoantibodies that bind to an epitope within residues 92-164 of humancTnI are detected.
 4. The method of claim 3, wherein autoantibodies thatbind to epitopes within residues 92-101, 127-136, or 155-164 of humancTnI are detected
 5. A method for diagnosing the presence of, or risk ofdeveloping, autoimmune heart disease in a subject, the methodcomprising: providing a sample comprising cardiac tissue of a subject;and detecting deposition of IgG autoantibodies on cardiac myocytes inthe sample, wherein the deposition of IgG autoantibodies indicates thatthe subject has or is at risk of developing autoimmune heart disease. 6.The method of claim 5, wherein the sample is an endomyocardial biopsy.7. The method of claim 5, wherein the subject has cardiac arrhythmia,idiopathic dilated cardiomyopathy, ischemic cardiomyopathy orunexplained heart failure.
 8. The method of claim 5, whereinautoantibodies that bind to an epitope within residues 92-164 of humancTnI are detected.
 9. The method of claim 8, wherein autoantibodies thatbind to epitopes within residues 92-101, 127-136, or 155-164 of humancTnI are detected
 10. A method for treating autoimmune heart disease,the method comprising: selecting a subject who has autoimmune heartdisease; and administering to the subject a therapy that depletes Blymphocytes in the subject.
 11. The method of claim 10, whereinselecting a subject comprises: providing a sample comprising serum of asubject; detecting the presence or absence in the sample of IgGautoantibodies to cardiac troponin I (cTnI), wherein the presence of IgGautoantibodies to cTnI indicates that the subject has or is at risk ofdeveloping autoimmune cardiomyopathy; selecting a subject who has IgGautoantibodies to cTnI.
 12. The method of claim 11, wherein the therapycomprises administration of an effective amount of rituximab or otherB-cell depleting or B-cell inactivating agents.
 13. The method of claim11, wherein the therapy comprises treating the subject withplasmapheresis or administering intravenous immunoglobulin.
 14. A methodfor monitoring the efficacy of a treatment for autoimmune heart disease,the method comprising: providing a first sample comprising serum of asubject; detecting a level of IgG autoantibodies to cardiac troponin I(cTnI) in the first sample, administering a therapy to the subject;providing a subsequent sample comprising serum of a subject; detecting alevel of IgG autoantibodies to cTnI in the subsequent sample; comparingthe level of IgG autoantibodies to cTnI in the first sample to the levelof IgG autoantibodies to cTnI in the subsequent sample, wherein adecrease in level of IgG4 autoantibodies to cTnI from the first to thesubsequent sample indicates that the therapy is effective.
 15. Themethod of claim 14, wherein the therapy comprises administration of aneffective amount of rituximab or other B-cell depleting or B-cellinactivating agents.
 16. The method of claim 14, wherein the therapycomprises treating the subject with plasmapheresis or administeringintravenous immunoglobulin.
 17. The method of claim 1, wherein the IgGantibodies are IgG4 subclass.
 18. The method of claim 5, wherein the IgGantibodies are IgG4 subclass.
 19. The method of claim 11, wherein theIgG antibodies are IgG4 subclass.
 20. The method of claim 14, whereinthe IgG antibodies are IgG4 subclass.